A method and system for controlling a plant process are disclosed. In process control systems, proportional-integral-derivative (PID) control has been used for process feedback control. A process response is fed back to a PID controller used to adjust a variable, such as a temperature, pressure or flow rate of the process. The PID controller uses the feedback to, for example, adjust an output command to the process for purposes of keeping the process stable.
The PID controller is configured using settings relating to the process. For example, a gain is established in each path of the PID controller (that is, the proportional (P) path, the integral (I) path and/or the derivative (D) path). The settings are manually selected by running tests on the actual process. The manual selection involves having detailed knowledge of the process. The settings can be manually updated from time-to-time by re-running the tests.
Automatic updating of PID controller settings has been performed off-line and/or using a model of the process being controlled. To accurately model the plant, PID hardware controllers are provided which are limited to individual loops, and which are dedicated to a particular process variable of the plant. Dedicated, individual loop controllers are used, at least in part, because they simplify the modeling of the process.